> Just wondering if anything like this 'hex file decoder' has been
> done before using the PIC?

That's funny! I have built the same type of programmer >1 year ago.
I named it PDA84 because I made it for use with my HP200LX. I`ve
implemented a small ASCII menu to choose erase/write/etc. The
hex file was sent as ASCII upload.

The problems I experienced was a) the 16550 UART sends 16 bytes out
in one go, ignoring RTS/CTS stop requests (at that time the C84
was widespread and loosing half your RAM for the FIFO is hard), and

b) as each byte in the target can be verified only immediately after
writing it, it is possible to have the whole code shifted by several
bytes in the target without noticing. At first I entered the prg
mode after "write" was selected by the user - while waiting for
the ASCII upload the target sometimes picked up noise on the clock
line (only RC targets).

I never finished the project (reading the target still misses, and
I wanted to implement XMODEM instead of ASCII send, as well as
rework the PCB) but would have done so if your company hired me :--)


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